JPH0226360B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a metal electrode support, a metal nozzle support and a single gas supply pipe leading to a dividing means, which divides the gas flow into a plasma generating gas. The present invention relates to a plasma torch of the kind that is split into a first stream and a second stream of cooling gas. This type of torch will be referred to below as a "monogas plasma torch".

Supplying plasma generating gas, electrodes, nozzles,
Utilizing a single circuit to cool the main elements of the torch, such as the insulator, is noteworthy as it reduces the complexity of the structure.

However, the need to control the ratio between the two streams in a precise manner despite significant temperature changes occurring during operation creates severe design problems. This is probably despite the fact that the principle has been worked out for many years (see FR 2275270).
This is likely the reason why no single gas plasma torch of any kind has been made industrially.

It is therefore an object of the invention to provide a monogas plasma torch which can operate in a satisfactory manner under the actual conditions of use.

To achieve this objective, the plasma torch according to the invention comprises a hollow electrode support supporting the electrodes and a single gas supply tube connected to the electrode support and supplying the gas flow. ,
a nozzle support; an insulator between the electrode support and the nozzle support; a nozzle supported by the nozzle support and forming a plasma-forming gas chamber together with the electrode support; dividing means for dividing into a flow of gas and a flow of cooling gas; means for directing said flow of plasma-forming gas into said plasma-forming gas chamber and said flow of cooling gas around a nozzle; and the dividing means comprises a set of plasma-forming gas orifices and a set of cooling gas orifices, both sets of orifices passing through a common metal part of the torch or close to each other. Penetrating another metal part of the torch that has a coefficient of expansion.

Particularly in embodiments where effective cooling of the electrode is desired, a tubular buffle is located within the electrode support, which directs the incoming gas first to the active portion of the electrode and then to a series of orifices. . In order to reduce the temperature of the cooling gas in this case, the cooling gas is guided between a nozzle support and an annular skirt having at least one perforation for sucking in outside air, and a replenishment channel is provided in which the gas supply pipe is routed through the gas supply pipe. connected to the part of the cooling circuit located downstream of the
or either of the above.

Embodiments of the present invention will be described below with reference to the drawings.

The plasma cutting torch shown has a handle 1 and a cutting head 2 at one end thereof, which together form a rotating body about an axis X--X. For the sake of simplicity, it is assumed that the axis X--X is vertical and that the head 2 points downward.

The handle 1 houses a single tube 3 for supplying gas and cutting current surrounded by an insulating envelope 4 and an electrical cable 5. The head 2 includes a first metal assembly 6 electrically connected to the tube 3, a second metal assembly 7 electrically connected to the cable 5, and an insulator 8 interposed between these assemblies 7 and 8. to accommodate.

The assembly 6 consists of three hollow elements. The first hollow element, the electrode support 9, has an axial blind bore 10 that opens at its lower end and communicates with the tube 3 via a radial gas inlet 11 at its other end. The second hollow element, the non-consumable electrode 12, is formed by a cut 13, the upper end of which is screwed into the lower end of the electrode support 9, and the bottom of which has an upwardly directed projection 14. This projection is provided with a blind seat 15 that opens at the bottom and accommodates an insert 16 made of zirconium, for example. The upper end of the tubular buttful 17, which is the third hollow element, is directly below the gas inlet 11 and the tube (blind hole) 1 of the electrode support 9.
0, the lower end of the tubular buffle 17 is enlarged to overlie the protrusion 14 of the electrode at a short distance from it.

The electrode support 9 has a stepped external shape. In the area of the gas inlet 11, its upper part ends in a horizontal shoulder 18, and an intermediate part of slightly smaller diameter follows this. The intermediate part is connected by a second horizontal shoulder 19 to the lower part, which lower part has a significantly smaller diameter approximately equal to the outer diameter of the cut 13. Four radial orifices 20, located at 90° to each other, pass through the electrode support 9 directly below the shoulder 19, and two orifices 2 of smaller diameter, also radial, pass through the electrode support 9 directly below the shoulder 19.
1 passes through the electrode support just above the upper edge of the cup 13.

The second metal assembly 7 consists of two elements: a tubular nozzle support 22 and a cup-shaped nozzle 23, the top edge of which is screwed into the lower end of the nozzle support, and the bottom of the nozzle with an axial orifice 24. penetrates.

Insulator 8, formed from a suitable insulating material, has three parts. The upper part of the insulator engages the middle part of the electrode support 9 and abuts the shoulder 18. The intermediate portion of the thick insulator defines a shoulder 19 and an annular chamber 25 through which a series of longitudinal passages 26 pass. The lower part of the insulator surrounds the electrode support with an annular gap in the area of the orifice 21. The annular chamber 25 also communicates with the upper end of the channel (blind hole) 10 of the electrode support by one or more refill channels 27 .

The nozzle support 22 consists of an upper part that engages around the middle and upper parts of the insulator 8, a thicker middle part that engages around the lower part of this insulator, and a lower part that receives the nozzle. The middle part of the nozzle support, together with the middle part of the insulator, defines an annular chamber 28 through which a series of longitudinal passages 29 pass. These longitudinal passages 29 lead into the last annular chamber 30, which is delimited on the inside by the lower part of the nozzle support 22 and the nozzle and on the outside by the nozzle support by screw fittings or other means. It is defined by an insulating skirt that is fixed to the upper part of the body. Several ventilation holes 3 pass through this skirt 31
2 is inclined inwardly and downwardly.

The torch is completed by an insulating sheath 33 of plastic material, which forms the outer part of the handle 1 and the head 2 up to the level of the top edge of the skirt 31.

During operation, the assembly 6 is raised by the tube 3 to a suitable potential compared to the article to be cut (not shown), the assembly 7 is raised to an intermediate potential by the cable 5, and a suitable gas, e.g. Compressed air is directed into tube 3.

Essentially, the gas enters the passageway 10 through the inlet 11 and descends through the butthole 17 and into the protrusion 1 of the electrode.
Pass around 4, Kup 13 and Batsuful 17
and then rises again in the annular space 34 existing between the buttful and the wall of the passageway 10.

A relatively low proportion (for example 10%) of the gas emerges from the annular space 34 through two orifices 21 and fills the annular gap provided at this level between the electrode support 9 and the insulator 8. A jet of plasma-forming gas is produced which is directed in and then into the annular chamber left free between nozzle 23 and cup 13 below the insulator. This plasma-forming gas exits the head 2 through a central orifice 24.

The remainder of the gas reaching the annular space 34 is used to cool the head 2 and in particular the nozzle 23. This gas emerges from the electrode support through an orifice 20 and then into an annular chamber, a passage 26, an annular chamber 2
8, into the passageway 29 and the annular chamber 30, from where it is discharged downwardly into the external atmosphere. A particular flow of gas proceeds directly from the inlet 11 through the passage 27 of the electrode support into the annular chamber 25, and a flow of cooling gas into the annular chamber 30 is carried out through the skirt 31.
A considerable amount of outside air is sucked in through the apertures 32.

Clearly, the gas that is able to enter through the tube 3 thus has the initial effect of substantially cooling the electrode 12. Orifice 20 and Orifice 21
A portion of this gas formed by the ratio between the total cross-sectional areas of and heated by the electrodes is directed to form a plasma-forming gas. In operation, this latter gas thus has a high temperature which is not affected by possible changes in the temperature of the gas passing through the tube 3. This is advantageous as temperature is known to affect the cutting ability of the torch by increasing the temperature of the plasma forming gas, thereby increasing the cutting ability of the torch. The portion of the flow exiting through orifice 21 can be controlled in a precise manner since orifices 20 and 21 are all drilled in the same component that expands in a uniform manner. This is further advantageous if the electrode support is formed by several elements with closely spaced coefficients of expansion. Furthermore, these orifices, and in particular orifice 21, can easily be made to have a very small diameter since they are drilled into a metal element. In contrast, the passages 26 in the insulator 8, which are solely for conducting cooling gas, can have a much larger diameter than the orifice 20, since their diameter is not critical.

The fresh gas entering the cooling circuit through the passage 27 downstream of the orifice 20 and the fresh air sucked in through the apertures 32 can obtain at each level sufficiently cool cooling gas to serve in an effective manner. Do it like this. In particular, the gas entering through the channel 27 makes it possible to keep the insulator 8 at a temperature below the softening point of the particular plastic material, which is particularly advantageous for mass production. Also, the passage 27 is connected to the orifice 20 and 2.
Due to the fact that the holes are drilled in the same metal material as 1, a good control of the gas fraction diverted can be achieved in this way.

Although its advantages as a variant are actually small,
Dual orifices to achieve flow division can be formed in one or two metal elements forming the nozzle support. In this case, the electrode support no longer has an orifice 21 and the entire gas contained in the annular space 34 exits through the orifice 20 for partial re-ejection into the plasma-forming gas chamber. The principle of this variant is schematically illustrated in FIG. 1, where a passage 21A, shown in broken lines, connects the annular chamber 28 to the plasma-forming gas chamber and is drilled in the nozzle support 22. The lower part of the insulator 8 is omitted to enable this connection. In this variant, all gas flows are channeled through channels 29 and 2, which are all formed in the same metal element 22.
Divided by 1A.

The design of the torch according to the invention allows the orifices 20 and 21 to be given any given orientation.

[Brief explanation of drawings]

FIG. 1 is a sectional view through the axis of a manual plasma cutting torch according to the present invention, and FIG. 2 is a cross-sectional view of FIG.
FIG. 3 is a cross-sectional view of the electrode support taken along the line - in FIG. 1; In the drawing, 3 is a gas supply pipe, 8 is an insulator,
9 is an electrode support, 17 is a tubular buffle, 22 is a nozzle support, 20 and 21 are orifices, 27 is a passage, 31 is a skirt, and 32 is a perforation.

Claims (1)

[Scope of Claims] 1. A plasma torch which includes a hollow electrode support supporting an electrode, a single gas supply pipe connected to the electrode support and supplying a gas flow, and a nozzle support. an insulator between the electrode support and the nozzle support; a nozzle supported by the nozzle support and forming a plasma-forming gas chamber together with the electrode support; and dividing means for dividing into a flow of cooling gas; and means for directing said flow of plasma-forming gas into said plasma-forming gas chamber and said flow of cooling gas around a nozzle; The dividing means comprises a set of plasma-forming gas orifices and a set of cooling gas orifices, both sets of orifices passing through a common metal part of the torch or having coefficients of expansion close to each other. penetrating another metal part of the torch having;
A plasma torch featuring 2. The plasma torch according to claim 1, wherein said common metal part is said electrode support. 3. The plasma torch of claim 1, wherein said common metal part is said nozzle support. 4. A plasma torch according to claim 2, wherein a cooling gas orifice communicates with the entrance of a guide passage formed in the insulator. 5. Plasma torch according to claim 4, wherein the guide passage is formed by a set of axial perforations located in the insulator. 6. A tubular baffle is arranged in the electrode support, which directs the flow of the supplied gas first to the active part of the electrode and then to the two sets of orifices. plasma torch. 7. The cooling gas is guided between the nozzle support and an annular skirt surrounding the nozzle, the skirt comprising at least one perforation for sucking in outside air. The plasma torch according to any one of Item 6. 8. The plasma torch of claim 6, wherein a replenishment passage connects the gas supply pipe to a cooling circuit located downstream of the baffle.